Lourdes Martín

Effects of salt and temperature on proteolysis during ripening of Iberian ham

Fifty-five hams from Iberian pigs were processed using two different dry-curing techniques, traditional and modern. Salt content, non-protein nitrogen and its fractions (peptide, amino acid and volatile basic nitrogen) from Biceps femoris muscles were quantified. The existence of an overlapping effect of both temperature and salt content on the general non-protein nitrogen production was observed. The most intense proteolytic breakdown took place when higher temperatures were reached during the drying stage. The difference in salt concentration seems to contribute to generating different quantities in the non-protein nitrogen fractions. The inclusion at the end of the cellar stage of a stuffing period would permit increasing the accumulation of free amino acid in high salted hams.

Changes in intramuscular lipids during ripening of Iberian dry-cured ham

Thirty-one thighs were obtained from Iberian pigs fattened with acorns and were processed during 22 months in the traditional dry-curing process. Lipolysis affecting intramuscular fat during the processing of Iberian dry-cured ham has been analyzed by studying the changes of glycerides, phospholipids and free fatty acids in lipids from Biceps femoris muscle. Little change affected the fatty acid composition of glycerides during processing. A double-phased increase in the acidity values and a decrease in the quantity of fatty acids of phospholipids during the processing were observed. There seems to be a relationship between the extension of the lipolysis taking place during the maturing and the processing conditions and raw material used.

Free amino acids and other non-volatile compounds formed during processing of Iberian ham.

Fifty-five legs from Iberian pigs were traditionally processed into dry cured hams. Free amino acids and other non-volatile compounds in the water-soluble fraction from the biceps femoris muscle were analyzed by HPLC. At the drying stage and in the last months in the cellar the largest increases in these water-soluble compounds took place. There was a clear influence on free amino acid formation of salt content and on the formation of peptides of the temperature at each processing stage. As the amount of non-volatile compounds in the water-soluble fraction increases with processing time, their determination could provide a maturation index for Iberian ham.

Evolution of volatile aldehydes in Iberian ham matured under different processing conditions

To evaluate the influence of the Iberian ham processing conditions in the evolution of volatile aldehydes, 35 hams were processed in two plants following different conditions of relative humidity and temperature. For this, free fatty acids, peroxide values and volatile aldehydes were quantified in the hams. The highest increases in free fatty acids were noted during the drying stage in both processing plants. The drying period also revealed the greatest increase in peroxide values, where the highest values were in those hams processed at higher temperatures. The temperature during post-salting and drying had a marked influence on the formation of volatile aldehydes, being responsible for the differences in volatile compounds of matured hams.

Effects of stage of lactation and parity on somatic cell counts in milk of Verata goats and algebraic models of their lactation curves

Effect of stage of lactation and parity on somatic cell counts in milk was studied in 100 goats of the Verata breed (25 each in the first, second, third and fourth lactation) free of clinical mastitis. Counts from aliquot milk samples collected at 21 d intervals were used to evaluate the parameters of a cell count curve through the lactation with an incomplete gamma function according to Wood (1967): Y(n) = A × nb × ecn, where Y(n) is the average somatic cell counts (SCC) in the 210 d lactation, expressed in millions/ml. Cell counts varied from 0.92 × 106/ml in the 1st week and 0.57 × 106/ml in the 5th week to 1.81 × 106/ml in the 30th week of lactation. Average cell concentration was significantly affected (P < 0.05) by parity, and did tend to increase from the first (1.27 × 106 SCC/ml) to the fourth lactation (2.02 × 106 SCC/ml). The curve of somatic cell counts was the inverted image of the lactation curve. That is the reason why the curve was fitted by the incomplete gamma functions of Wood (R2 = 0.97). From their equations a minimum cell concentration (−(bc)) was deduced on the following days: first lactation, 28; second lactation, 55; third lactation, 13 and fourth lactation, 25. We observed that the estimation of inflection appearing in conjunction with the first and second months of lactation occurred in the same way as with yield and quality of milk.

Somatic cell types in goats milk in relation to total cell count, stage and number of lactation

Abstract Change in cell concentration and types of cells through lactation was studied in milk of 100 goats of the Verata breed (25 each in 1st, 2nd, 3rd and 4th lactations), with machine milking. The degree of participation of each cell type was analysed: (a) during 210 days of lactation; (b) as a function of number of lactations (1st to 4th); and (c) in relation to total cell count. Average percentages of the various cell types in milk of all animals were: 63.0% for polymorphonucleates, 16.2% macrophages, 7.2% lymphocytes, 13.0% remainder. Through the lactation the polymorphonucleate increased from 45.8% to 70.3%, while the rest of the cell types decreased. Polymorphonucleates increased from 51.5% (in the 1st lactation) to 69.3% (in the 4th lactation), and macrophages decreased (20.0% to 14.4%), as did lymphocytes (12.5% to 4.7%) and degenerated cells (16.3% to 13.0%). Correlation coefficients reached statistical significance in all cases.

Fatty acid composition of Verata goat kids fed either goat milk or commercial milk replacer

Fatty acid composition of perirenal fat of young Verata male and female kids fed with natural milk and with three concentrations of commercial milk replacer was studied. There was no effect associated with sex. In each gender the only statistical difference in fatty acid composition between the four feeding groups under study were pentadecanoic acid (C15:0), heptadecanoic acid (C17:0) and heptadecenoic acid (C17:1) which were higher in all cases in naturally fed kids (P < 0.05). The origin of odd-numbered fatty acids in depot fats of goat kids is discussed considering the possible role of microbial rumen synthesis in goat kids or the direct incorporation from the milk (or milk replacer) fat. The relatively low stearic concentration in perirenal fat in all groups (around 15%) suggest low ruminal activity. Determination of C15:0, C17:0 and C17:1 in perirenal fat could help differentiate the feeding system of young kids and might be useful for identification purposes of goat kid carcasses.

Influencia de las condiciones de elaboración sobre la proteolisis durante la maduración del jamón ibérico Influence of the processing conditions of Iberian ham on proteolysis during ripening

Non-protein nitrogen and its fractions (peptides, amino acids and volatile basic nitrogen) were determined in biceps femoris and semimembranosus muscles of two homogeneous groups of Iberian dry-cured ham in different stages of maturation, and ripened in two different factories under different environmental conditions. A progressive increase in non-protein nitrogen was observed during ripening in all groups, being especially intense during the drying stage, when the temperature was the highest during maturation. During the first stages of processing, the proportion of peptides and free amino acids remained similar while free amino acids increased more markedly from the drying stage, representing the largest fraction at the end of the process. Volatile basic nitrogen was the least abundant fraction of non-protein nitrogen during ripening. Hams kept at higher temperature during longer periods, and with lower salt content, produced larger amounts of all three fractions of non-protein nitrogen in fully ripened dry-cured Iberian ham.

Characterisation of the most odour-active compounds of bone tainted dry-cured Iberian ham.

The most odour-active compounds of different bone tainted dry-cured Iberian hams were researched using the detection frequency method. Most of the odourants identified were found in all the Iberian hams (spoiled and unspoiled). Some compounds (ethyl butanoate, dimethyl disulfide, phenylacetaldehyde, acetic, propanoic, butanoic, 3-methylbutanoic and pentanoic acids) were identified in the spoiled hams as Iberian ham odourants for the first time. The detection frequency (DF) values for the spoiled and the unspoiled hams were markedly different. The main differences were found for 2-methylpropanal, ethyl-2-methylpropanoate, ethyl-2-methylbutanoate, phenylacetaldehyde and methional (the lowest DF values were found in the unspoiled ham) and hexanal (the largest DF value was found in the unspoiled ham). Spoiled hams with a different global odour had different DF values.

Effect of protected fat supplementation to lactating goats on growth and fatty acid composition of perirenal fat in goat kids

An experiment was conducted to measure the response of goat kids to supplementary feeding of their dams with protected fat (calcium soap of fatty acids). At birth, 22 single male goat kids were distributed in two groups according to the dams’ diet supplemented with 0 (dam control diet, DCD) or 100 (dam protected fat, DPF) g/day of protected fat through lactation. Higher energy intake of dams given protected fat caused higher fat content of their milk ( P P P P P > 0Ό5) in terms of kid mean live-weight gain, being 172 g (DPF) compared with 148 g (DCD). Fatty acid composition of the perirenal fat showed some differences between groups. Fat composition of group DPF was significantly higher in palmitoleic, oleic and linoleic acid content. In addition, myristic, palmitic and stearic acid had lower values. Fat of goat kids of the DPF group was more unsaturated (43·3 g per 100 g) than fat from animals of the DCD group (32·5 g per 100 g). In the DPF group, oleic acid comprised most of the unsaturated fatty acid due to its important increase compared with fat composition of the DCD group. In conclusion, fatty acid composition of fat depot in goat kids can he modified by feeding of the dams through lactation, which could be useful for possible changes according to market demand.